41 research outputs found
Characterization methods dedicated to nanometer-thick hBN layers
Hexagonal boron nitride (hBN) regains interest as a strategic component in
graphene engineering and in van der Waals heterostructures built with two
dimensional materials. It is crucial then, to handle reliable characterization
techniques capable to assess the quality of structural and electronic
properties of the hBN material used. We present here characterization
procedures based on optical spectroscopies, namely cathodoluminescence and
Raman, with the additional support of structural analysis conducted by
transmission electron microscopy. We show the capability of optical
spectroscopies to investigate and benchmark the optical and structural
properties of various hBN thin layers sources
Quantum well confinement and competitive radiative pathways in the luminescence of black phosphorus layers
Black phosphorus (BP) stands out from other 2D materials by the wide
amplitude of the band-gap energy (Delta(Eg)) that sweeps an optical window from
Visible (VIS) to Infrared (IR) wavelengths, depending on the layer thickness.
This singularity made the optical and excitonic properties of BP difficult to
map. Specifically, the literature lacks in presenting experimental and
theoretical data on the optical properties of BP on an extended thickness
range. Here we report the study of an ensemble of photoluminescence spectra
from 79 passivated BP flakes recorded at 4 K with thicknesses ranging from 4 nm
to 700 nm, obtained by mechanical exfoliation. We observe that the exfoliation
steps induce additional defects states that compete the radiative recombination
from bound excitons observed in the crystal. We also show that the evolution of
the photoluminescence energy versus thickness follows a quantum well
confinement model appreciable from a thickness predicted and probed at 25 nm.
The BP slabs placed in different 2D heterostructures show that the emission
energy is not significantly modulated by the dielectric environment.
Introduction Confinement effectsComment: 11 pages, 3 figures - Main text 12 pages, 5 figures - Supporting
informatio
Distinguishing different stackings in layered materials via luminescence spectroscopy
Despite its simple crystal structure, layered boron nitride features a
surprisingly complex variety of phonon-assisted luminescence peaks. We present
a combined experimental and theoretical study on ultraviolet-light emission in
hexagonal and rhombohedral bulk boron nitride crystals. Emission spectra of
high-quality samples are measured via cathodoluminescence spectroscopy,
displaying characteristic differences between the two polytypes. These
differences are explained using a fully first-principles computational
technique that takes into account radiative emission from ``indirect'',
finite-momentum, excitons via coupling to finite-momentum phonons. We show that
the differences in peak positions, number of peaks and relative intensities can
be qualitatively and quantitatively explained, once a full integration over all
relevant momenta of excitons and phonons is performed.Comment: Main: 6 pages and 4 figures, Supplementary: 6 pages and 7 figure
Distinguishing Different Stackings in Layered Materials via Luminescence Spectroscopy
peer reviewedDespite its simple crystal structure, layered boron nitride features a surprisingly complex variety of phonon-assisted luminescence peaks. We present a combined experimental and theoretical study on ultraviolet-light emission in hexagonal and rhombohedral bulk boron nitride crystals. Emission spectra of high-quality samples are measured via cathodoluminescence spectroscopy, displaying characteristic
differences between the two polytypes. These differences are explained using a fully first-principles computational technique that takes into account radiative emission from “indirect,” finite-momentum excitons via coupling to finite-momentum phonons.We show that the differences in peak positions, number of peaks, and relative intensities can be qualitatively and quantitatively explained, once a full integration over all relevant momenta of excitons and phonons is performed
Etude des propriétés optiques de nanoparticules de silicium et de leur interface avec une matrice de silice par ellipsométrie et spectroscopie de déflexion photothermique
PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF
A spin crossover porous hybrid architecture for potential sensing applications
International audienc
The challenging road of freestanding (100) n-type diamond: The challenging road of freestanding (100) n-type diamond
International audienc
Electrical properties of n-type phosphorus-doped diamond grown on (113) orientation compared to the conventional (111) and (100) orientations
International audienc